Polythiol composition, polymerizable composition for optical material and use thereof

ABSTRACT

A polythiol composition includes a polythiol compound (a) represented by the following formula (5) 
                         
and a compound (b) wherein, in a high performance liquid chromatography measurement of the polythiol composition under defined conditions, the peak area of the compound (b) which appears at the retention time from 4.3 minutes to 5.6 minutes is equal to or less than 3.0, with respect to the peak area of 100 of the polythiol compound (a) which appears at the retention time from 12.0 minutes to 13.5 minutes. A process for producing a polythiol composition, a method of manufacturing a molded product, a molded product, an optical element and a lens are also provided.

RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/686,970, filed on Aug. 25, 2017, now abandoned, which is aContinuation of U.S. application Ser. No. 14/395,146, filed on Oct. 17,2014, and issued as U.S. Pat. No. 9,777,103, which is a U.S. NationalStage of International Application No. PCT/JP2013/071891, filed on Aug.13, 2013, which in turn claims priority to Japanese Application No.2012-179899, filed on Aug. 14, 2012, and International Application No.PCT/JP2013/001201, filed on Feb. 28, 2013, the entire content of each ofwhich is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a polythiol composition, apolymerizable composition for an optical material and use thereof.

BACKGROUND ART

Since a plastic lens is lighter, hardly broken and capable of beingdyed, compared to an inorganic lens, the plastic lens has recentlybecome widely used rapidly in an optical element such as a spectaclelens or a camera lens.

Higher performance has been demanded for a resin for the plastic lensand high refractive index, high Abbe number, low density, highheat-resistance, or the like has been required. So far various kinds ofresin materials for the lens have been developed and used.

Among these, an optical material comprised of a polythiourethane-basedresin has high refractive index and high Abbe number, and is excellentin the impact resistance, the dyeability, the processability, or thelike. The polythiourethane-based resin can be obtained by reacting apolythiol with a polyiso(thio)cyanate compound, or the like.

In a case of using in the plastic lens, the polythiourethane-based resinis required to cause less coloration, have excellent resin color and betransparence. In a case where the quality of polythiol was deteriorated,there were cases where the quality of the obtained resin was alsodeteriorated.

Patent documents which relate to a process of producing polythiolinclude the following patent documents.

In Patent Document 1 or Patent Document 2, a method in which2-mercaptoethanol reacts with epichlorohydrin, the obtained compoundreacts with thiourea to obtain an isothiuronium salt, and next theisothiuronium salt is hydrolyzed to obtain the specific polythiolcompound is described.

In Patent Document 3, a process of producing a polythiol compound inwhich the amount of the specific impurities included in2-mercaptoethanol is set to the predetermined range is described.

In Patent Document 4, a process of producing a polythiol compound inwhich calcium content included in thiourea is set to the predeterminedrange is described.

RELATED DOCUMENT Patent Document

[Patent Document 1] Japanese Unexamined Patent Publication No. 2-270859

[Patent Document 2] Japanese Unexamined Patent Publication No. 7-252207

[Patent Document 3] PCT International Publication No. 2007/129449

[Patent Document 4] PCT International Publication No. 2007/129450

DISCLOSURE OF THE INVENTION

However, in a case where the plastic lens comprised of thepolythiourethane-based resin is produced by using the polythiol compoundobtained in the methods described in the documents, there was room forimprovement of optical properties such as color, transparency,striation.

The present inventors ascertained that a trace of the specific componentis included in the polythiol compound, as a result of extensive studiesin order to improve the optical properties, and found that the specificcomponent included at the predetermined amount affects the reaction(polymerization) activity in a reaction (polymerization reaction) of thepolythiol compound and a polyisocyanate compound.

The present invention can be given as below.

[1] A polythiol composition includes a polythiol compound (A) havingthree or more mercapto groups, and a nitrogen-containing compound (B) inwhich at least one of a mercapto group of the polythiol compound (A) isreplaced with a group represented by the following formula (a)

wherein, in the formula, * represents an atomic bonding,

and at least other one of a mercapto group of the polythiol compound (A)is replaced with a hydroxyl group, in which the peak area of thenitrogen-containing compound (B) is equal to or less than 3.0, withrespect to the peak area of 100 of the polythiol compound (A) in a highperformance liquid chromatography measurement.

[2] The polythiol composition according to [1], in which the polythiolcompound (A) is represented by the following formula (5).

[3] The polythiol composition according to [1], in which the polythiolcompound (A) is primarily comprised of at least one kind selected fromthe compounds represented by the following formulae (6) to (8).

[4] A polymerizable composition for an optical material includes thepolythiol composition according to any of [1] to [3] and apoly(thio)isocyanate compound.

[5] A method of manufacturing a molded product, comprising mixing thepolythiol composition according to any of [1] to [3] and apoly(thio)isocyanate compound to obtain a polymerizable composition foran optical material; and

putting the polymerizable composition into a mold and curing thecomposition.

[6] A molded product which is obtained by curing the polymerizablecomposition according to [4].

[7] An optical element comprised of the molded product according to [6].

[8] A lens which comprised of the optical element according to [7].

It is possible to obtain a plastic lens comprised of thepolythiourethane-based resin which is excellent in quality such ascolor, transparency, striation by using the polythiol composition of thepresent invention.

That is, according to the present invention, by setting thenitrogen-containing compound (B) which is a trace component included inthe polythiol composition to within the predetermined range, a plasticlens product in which the high quality such as color, transparency,striation, or the like is demanded can be industrially produced with asatisfactory yield. Furthermore, when the polymerizable composition isprepared, by adjusting the amount of the nitrogen-containing compound(B) included in the polythiol composition and further confirming theamount, it is possible to suppress the occurrence of defects in qualitysuch as striation or coloration of the plastic lens, and thus it ispossible to improve the yield of product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an HPLC chart of a polythiol composition obtained inExample A-1.

FIG. 2 shows a high performance liquid chromatography (HPLC) chart of apolythiol composition obtained in Example C-1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, description will be given of a polythiol composition of thepresent invention based on embodiments.

The polythiol composition of the present embodiment includes a polythiolcompound (A) and a nitrogen-containing compound (B). Hereinafter,description will be given of each component.

(Polythiol Compound (A))

The polythiol compound (A) is a polythiol compound having three or moremercapto groups.

A polythiol compound (A) includes an aliphatic polythiol compound suchas 1,2,3-propanetrithiol, tetrakis(mercaptomethyl)methane,trimethylolpropane tris(2-mercaptoacetate), trimethylolpropanetris(3-mercaptopropionate), trimethylolethane tris(2-mercaptoacetate),trimethylolethane tris(3-mercaptopropionate), pentaerythritoltetrakis(2-mercaptoacetate), pentaerythritoltetrakis(3-mercaptopropionate), 1,2,3-tris(mercaptomethylthio)propane,1,2,3-tris(2-mercaptoethylthio)propane,1,2,3-tris(3-mercaptopropylthio)propane,4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane,5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,tetrakis(mercaptomethylthiomethyl)methane,tetrakis(2-mercaptoethylthiomethyl)methane,tetrakis(3-mercaptopropylthiomethyl)methane,bis(2,3-dimercaptopropyl)sulfide, ester of these polythiols and thethioglycolic acids or mercaptopropionic acid,1,1,3,3-tetrakis(mercaptomethylthio)propane,1,1,2,2-tetrakis(mercaptomethylthio)ethane,4,6-bis(mercaptomethylthio)-1,3-dithiacyclohexane,tris(mercaptomethylthio)methane, and tris(mercaptoethylthio)methane; anaromatic polythiol compound such as 1,3,5-trimercaptobenzene,1,3,5-tris(mercaptomethyl)benzene,1,3,5-tris(mercaptomethyleneoxy)benzene,1,3,5-tris(mercaptoethyleneoxy)benzene.

However, the polythiol compound (A) is not limited to only the exemplarycompounds.

In the present embodiment, as a polythiol compound (A), a polythiolcompound which is primarily comprised of at least one kind selected fromthe group consisting of

-   4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane represented by the    following formula (5),-   4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane    represented by the following formula (6),-   4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane    represented by the following formula (7), and-   5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane    represented by the following formula (8) can be preferably used.

(Nitrogen-Containing Compound (B))

The nitrogen-containing compound (B) has a structure in which at leastone of a mercapto group of the polythiol compound (A) having three ormore mercapto groups is replaced with a group represented by thefollowing formula (a) and at least one other mercapto group of thepolythiol compound (A) is replaced with a hydroxyl group.

In the formula, * represents an atomic bonding.

Moreover, the nitrogen-containing compound (B) can include a salt of thecompound having the structure described above. The salt is notparticularly limited, however, for example, includes carboxylic acidsuch as acetic acid, an organic acid such as methanesulfonic acid, acompound having a mercapto (SH) group, an inorganic acid such ashydrochloric acid, sulfuric acid or phosphoric acid.

In the polythiol composition of the present embodiment, the peak area ofthe nitrogen-containing compound (B) to the peak area of 100 of thepolythiol compound (A) (hereinafter, also referred to simply as “theratio of the peak area of the nitrogen-containing compound (B)”) isequal to or less than 3.0, preferably equal to or less than 1.5, andmore preferably equal to or less than 0.50 in a high performance liquidchromatography measurement. The lower limit of the ratio of the peakarea of the nitrogen-containing compound (B) does not particularlyexist, however, is preferably equal to or more than 0.01, consideringthe number of step in purification in an industrial production scale.

In the usual case, the nitrogen-containing compound (B) is a mixture ofa plurality of isomers, and appears as a peak at the predeterminedretention time in high performance liquid chromatography. Moreover, thepeaks of the nitrogen-containing compound (B) which is a mixture of aplurality of isomers may be overlapped.

By setting the ratio of the peak area of the nitrogen-containingcompound (B) to the range described above, it is possible to obtain theplastic lens comprised of the polythiourethane-based resin which isexcellent in quality such as color, transparency, striation.

The ratio of the peak area of the nitrogen-containing compound (B) canbe calculated from the following expression based on the peak area ofhigh performance liquid chromatography.Expression: {[peak area of nitrogen-containing compound (B)]/[peak areaof polythiol compound (A)]}×100

Moreover, the conditions of high performance liquid chromatography areappropriately selected according to structures, properties, or the likeof the polythiol compound (A) and the nitrogen-containing compound (B).

The ratio of the peak area of the nitrogen-containing compound (B) inthe present embodiment, for example, can be described, in a case wherethe polythiol compound (A) is“4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane” and thenitrogen-containing compound (B) is “a compound in which one of amercapto group of the polythiol compound (A) is replaced with a grouprepresented by the formula (a) described above and other one of amercapto group is replaced with a hydroxyl group.

In a case of measuring by high performance liquid chromatography underthe conditions described below and calculating the ratio of the peakarea of the nitrogen-containing compound (B) based on the expressiondescribed above, the peak area of the nitrogen-containing compound (B)which appears at the retention time from 4.3 minutes to 5.6 minutes isequal to or less than 3.0, preferably equal to or less than 1.0, andmore preferably equal to or less than 0.50, with respect to the peakarea of 100 of the polythiol compound (A) which appears at the retentiontime from 12.0 minutes to 13.5 minutes. The lower limit of the ratio ofthe peak area of the nitrogen-containing compound (B) does notparticularly exist, however, is preferably equal to or more than 0.01,considering the number of step in purification in an industrialproduction scale.

Moreover, in a case of measuring under the conditions described below,any peak of the nitrogen-containing compound (B) which is a mixture of aplurality of isomers appears within the retention time described aboveand each peak may be overlapped.

Measurement conditions of high performance liquid chromatography

Column: YMC-Pack ODS-A A-312 (S5Φ6 mm×150 mm)

Mobile phase: acetonitrile/0.01 mol-potassium dihydrogen phosphateaqueous solution=60/40 (vol/vol)

Column temperature: 40° C.

Flow rate: 1.0 ml/min

Detector: UV detector, wavelength 230 nm

Preparation of measurement solution: 160 mg of a sample is dissolved andmixed in 10 ml of acetonitrile.

Injection volume: 2 μL

Furthermore, the ratio of the peak area of the nitrogen-containingcompound (B) in the present embodiment, for example, can also bedescribed in a case where the polythiol compound (A) is “a polythiolcompound which is primarily comprised of at least one kind selected fromthe group consisting of5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane” and thenitrogen-containing compound (B) is “a compound in which one of amercapto group of the polythiol compound (A) is replaced with a grouprepresented by the formula (a) described above and other one of mercaptogroup is replaced with a hydroxyl group”.

In a case of measuring by high performance liquid chromatography underthe conditions described below and calculating the ratio of the peakarea of the nitrogen-containing compound (B) based on the expressiondescribed above, the peak area of the nitrogen-containing compound (B)which appears at the retention time from 6.5 minutes to 8.0 minutes isequal to or less than 3.0, preferably equal to or less than 2.0, andmore preferably equal to or less than 1.5, with respect to the peak areaof 100 of the polythiol compound (A) which appears at the retention timefrom 22.0 minutes to 28.0 minutes. The lower limit of the ratio of thepeak area of the nitrogen-containing compound (B) does not particularlyexist, however, is preferably equal to or more than 0.01, consideringthe number of step in purification in an industrial production scale.

Moreover, in a case of measuring under the conditions described below,any peak of the nitrogen-containing compound (B) which is a mixture of aplurality of isomers appears within the retention time described aboveand each peak may be overlapped.

Measurement conditions of high performance liquid chromatography

Column: YMC-Pack ODS-A A-312 (S5Φ6 mm×150 mm)

Mobile phase: acetonitrile/0.01 mol-potassium dihydrogen phosphateaqueous solution=60/40 (vol/vol)

Column temperature: 40° C.

Flow rate: 1.0 ml/min

Detector: UV detector, wavelength 230 nm

Preparation of measurement solution: 160 mg of a sample is dissolved andmixed in 10 ml of acetonitrile.

Injection volume: 2 μL

By setting the ratio of the peak area of the nitrogen-containingcompound (B) to the range described above, it is possible to obtain theplastic lens comprised of the polythiourethane-based resin which isexcellent in quality such as color, transparency and striation.

As described above, in the present embodiment, by giving two types ofthe polythiol compound described above as a polythiol compound (A), asan example, a case where the nitrogen-containing compound (B) is “acompound in which one of a mercapto group of two types of the polythiolcompound described above is replaced with a group represented by theformula (a) described above and other one of a mercapto group isreplaced with a hydroxyl group” has been described, however, aspectsincluding the nitrogen-containing compound (B) as (1) or (2) describedbelow may also be included.

(1) The nitrogen-containing compound (B) in which at least one of amercapto group of two types of the polythiol compound described above isreplaced with a group represented by the formula (a) described above andat least two mercapto groups are replaced with a hydroxyl group.

(2) The nitrogen-containing compound (B) in which at least two of amercapto group of two types of the polythiol compound described aboveare replaced with a group represented by the formula (a) described aboveand at least one of a mercapto group is replaced with a hydroxyl group.

In addition, in the present embodiment, a case where the polythiolcompound (A) are two types of the polythiol compound described above isgiven as an example to be described, however, a polythiol compoundexcept these two types selected from the exemplified polythiol compounddescribe above can also be used.

<Process for Producing Polythiol Composition>

The polythiol composition of the present embodiment can be produced bythe following steps.

Step A: The polyalcohol compound is obtained.

Step B: The polyalcohol compound obtained in the step A reacts withthiourea in the presence of hydrogen chloride to obtain an isothiuroniumsalt.

Step C: while a reaction solution including the isothiuronium saltobtained in the step B is maintained at the temperature from 20° C. to60° C., aqueous ammonia is added into the reaction solution within 80minutes and the isothiuronium salt is hydrolyzed at the temperature from20° C. to 60° C. to obtain the polythiol composition.

Step D: The polythiol composition obtained in the step C is purified.

In the present embodiment, the cases where the polythiol compositionsincluding two types of the polythiol compound described below areobtained are described.

As a polythiol compound, a case of producing “a polythiol compound whichis primarily comprised of4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctan” is set to an embodimentI and a case of producing “a polythiol compound which is primarilycomprised of at least one kind selected from the group consisting of4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane” is set to anembodiment II to be described.

Embodiment I

Hereinafter, each step will be described in order.

(Step A)

In the step A, a 2-mercaptoethanol reacts with an epihalohydrin compoundrepresented by the following formula (1), thereby it is possible toobtain a triol compound represented by the following formula (2) as apolyalcohol compound.

In the formula (1), X is a halogen atom which is a fluorine atom, achlorine atom, a bromine atom, or an iodine atom, and preferably achlorine atom.

In the present embodiment, the reaction can be performed in a range from10° C. to 50° C., preferably from 15° C. to 50° C., and more preferablyfrom 25° C. to 45° C. The reaction temperature is lower than 10° C.,since the reaction does not progress in the first half of the reaction,unreacted materials are stagnated in the reaction system, and thus thereare cases where the reaction rapidly progress. When higher than 50° C.,there are cases where color of the lens degenerates. That is, when in arange of the temperature described above, the controllability of thereaction is excellent, further color of the obtained plastic lens isalso excellent.

The reaction can be performed for 2 hours to 12 hours, and preferablyfor 3 hours to 10 hours.

The reaction described above, for example, can be performed as follows.Firstly, after 2-mercaptoethanol and a base are added into water orlower alcohol solvent such as methanol, or ethanol as necessary,epihalohydrin is added dropwise to perform the reaction. It ispreferable to adjust so that the reaction temperature and the reactiontime are in the ranges described above. Moreover, the reaction timeincludes the time of adding dropwise of epihalohydrin, and thetemperature of the reaction solution needs to be adjusted to thereaction temperature described above when adding dropwise. The usedamount of 2-mercaptoethanol is more preferably equal to or more than 1.9mol and equal to or less than 2.1 mol, with respect to 1 mol ofepihalohydrin.

As a base, a metal hydroxide such as sodium hydroxide, potassiumhydroxide, a metal carbonate such as sodium carbonate, potassiumcarbonate, and a tertiary amine such as triethylamine, tributylamine areincluded, however, sodium hydroxide is most preferable, in the light ofthe reactivity and the economy. In a case of a monovalent base, the usedamount of the base is equal to or more than 0.5 mol and equal to or lessthan 2 mol, and preferably equal to or more than 0.9 mol and equal to orless than 1.1 mol, with respect to 1 mol of epihalohydrin. In a case ofa bivalent base, the half amount of the used amount of a monovalent baseis preferable. The base can be used as an aqueous solution, an alcoholsolution, or the like, and in a case of using as a solution, theconcentration of the base can be appropriately selected.

In addition, except the method described above, by the two-stagereaction in which once diol is produced represented by the followingformula (3), thereafter 2-mercaptoethanol is added dropwise, it is alsopossible to obtain the triol compound represented by the formula (2).

In the method, firstly, 2-mercaptoethanol reacts with an epihalohydrincompound represented by the formula (1) described above to obtain acompound represented by the following formula (3).

The reaction temperature is from 10° C. to 20° C. The reaction time isfrom approximately 2 hours to 10 hours.

Next, the compound described above represented by the formula (3) reactswith 2-mercaptoethanol to obtain the triol compound represented by theformula (2). The reaction temperature is from 10° C. to 50° C.,preferably 15° C. to 50° C., and more preferably 20° C. to 45° C. Thereaction time is from approximately 2 hours to 12 hours.

By performing the steps in a range of the temperature described above,the controllability of the reaction is excellent.

Specifically, the method can be performed as follows.

Firstly, epihalohydrin is added dropwise into a solution comprised of2-mercaptoethanol, and water or lower alcohol solution such as methanolor ethanol as necessary, and an aqueous solution of the base of thecatalyst quantity or lower alcohol such as methanol or ethanol solutionof the base of the catalyst quantity. It is preferable to adjust so thatthe reaction temperature and the reaction time are in the rangesdescribed above. In the solution to which epihalohydrin is addeddropwise, the used amount of 2-mercaptoethanol is equal to or more than1 mol and equal to or less than 3 mol, and preferably equal to or morethan 1 mol and equal to or less than 2 mol, with respect to 1 mol ofepihalohydrin. In addition, the base described above of the catalystquantity is used, and in a case of a monovalent base, the used amount ofthe base described above is equal to or more than 0.001 mol and equal toor less than 0.1 mol, with respect to epihalohydrin. In a case of abivalent base, the half amount of the used amount of a monovalent baseis preferable. The base can be used as an aqueous solution, an alcoholsolution, or the like, and in a case of using as a solution, theconcentration of the base can be appropriately selected. Byepihalohydrin being added dropwise into the solution described above,diol represented by the formula (3) is obtained.

Subsequently, by further adding 2-mercaptoethanol so that2-mercaptoethanol is equal to or more than 1.5 mol and equal to or lessthan 3.0 mol, with respect to 1 mol of epihalohydrin if there is anyshortage, and by further adding the shortage of the base so that thebase is equal to or more than 1.0 mol and equal to or less than 2.0 mol,with respect to epihalohydrin, the polyalcohol compound represented bythe formula (2) can be obtained. It is preferable to adjust so that thereaction temperature and the reaction time are in the ranges describedabove.

In a synthesis of diol represented by the formula (3), in a case where astrong base such sodium hydroxide is used, it is appropriate for thereaction temperature to be set to equal to or more than 10° C. and equalto or less than 50° C. The reaction temperature is too high, since thebase added with the catalyst quantity is consumed in a producingreaction of the polyalcohol compound from diol, there is somepossibility of decreasing the yield of a diol.

(Step B)

Next, the polyalcohol compound represented by the formula (2) obtainedin the step A reacts with thiourea in the presence of hydrogen chlorideto obtain the isothiuronium salt.

Specifically, thiourea which is equal to or more than 2.7 mol,preferably equal to or more than 2.7 mol and equal to or less than 6.0mol, and more preferably equal to or more than 2.9 mol and equal to orless than 3.2 mol, with respect to 1 mol of the polyalcohol compound, isadded to the polyalcohol compound represented by the formula (2) toreact. The reaction is performed in the presence of hydrogen chloridewhich is equal to or more than 3 mol, preferably equal to or more than 3mol and equal to or less than 12 mol, and more preferably equal to ormore than 3 mol and equal to or less than 5 mol, with respect to 1 molof the polyalcohol compound, in a range from room temperature to thereflux temperature, and preferably at the temperature from 90° C. to120° C., for approximately 1 hour to 10 hours. By the reaction of thepolyalcohol compound and thiourea, the isothiuronium salt compound isformed. By using hydrogen chloride, it is possible to obtain thesufficient reaction speed, furthermore, control the coloration of thethiol compound and color of the obtained plastic lens. As hydrogenchloride, a hydrochloric acid aqueous solution and hydrogen chloride gascan be used. In a case of using a hydrochloric acid aqueous solution,the concentration thereof can be appropriately selected.

(Step C)

Aqueous ammonia is added into the reaction solution including theisothiuronium salt obtained in the step B, and the isothiuronium salt ishydrolyzed to obtain the polythiol compound. As a polythiol compound, itis possible to obtain the polythiol composition which is primarilycomprised of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctanerepresented by the following formula (5).

Specifically, while the reaction solution including the isothiuroniumsalt is maintained in a range of the temperature from 15° C. to 60° C.,preferably from 31° C. to 55° C., more preferably from 31° C. to 45° C.,aqueous ammonia is added into the reaction solution for equal to orshorter than 80 minutes, preferably for equal to or shorter than 70minutes, and more preferably from 20 minutes to 60 minutes. The time ofadding aqueous ammonia is preferably shorter, however, the time is setto within the time described above, considering the equipment capacitysuch as coolability, or the like.

Before adding aqueous ammonia, an organic solvent is preferably added.By adding the organic solvent, the quality such as color of the obtainedplastic lens is improved. The additive amount of the organic solvent isappropriately selected according to the classification of the solvent,or the like, however, it is possible to add with the amount which isfrom 0.1 times to 3.0 times, and preferably from 0.2 times to 1.0 time,with respect to the thiuronium salt reaction solution. As an organicsolvent, toluene, xylene, chlorobenzene, dichlorobenzene, and the likeare included. Toluene is preferable from the viewpoint of the effectdescribed above.

Aqueous ammonia can be added within the addition time described above sothat ammonia (NH₃) is equal to or more than 1 mol, preferably equal toor more than 1 mol and equal to or less than 3 mol, and more preferablyequal to or more than 1.1 mol and equal to or less than 2 mol, with 1mol of the used amount of hydrogen chloride described above. Theconcentration of aqueous ammonia can be set to from 10% to 25%. Inaddition, ammonia gas can be used instead of aqueous ammonia. In a casewhere ammonia gas is added in place of all or part of aqueous ammonia,it is possible to perform in the same conditions (the used amount, theaddition time, the addition temperature) as aqueous ammonia.

In the present embodiment, ammonia (NH₃) is added so that the additionrate is equal to or more than 1.25 mol %/minute, preferably equal to ormore than 1.25 mol %/minute and equal to or less than 3.75 mol %/minute,and more preferably equal to or more than 1.38 mol %/minute and equal toor less than 2.5 mol %/minute, with 1 mol of hydrogen chloride. In thestep, it is not necessary to continuously add with the rate describedabove, and the average addition rate in the addition time describedabove only has to be included in the range.

And, after aqueous ammonia is added, a hydrolysis reaction is continuedto be performed in a range from room temperature to the refluxtemperature, and preferably from 30° C. to 80° C., for approximately 1hour to 8 hours.

(Step D)

In the present embodiment, the polythiol composition obtained in thestep C is purified by washing.

Specifically, acid washing and then plural times of aqueous washing canbe performed. Aqueous washing before acid washing and alkaline washingafter acid washing can be performed. It is possible to decrease thenumber of times of aqueous washing by alkaline washing. By a washingstep, it is possible to effectively remove impurities, or the like. Bypurifying by means of washing, it is possible to produce the plasticlens of high quality in which color of the plastic lens obtained fromthe polythiol composition is improved, further the occurrence ofclouding and striation is decreased, in a satisfactory yield, and theefficiency percentage is also improved. As an example of the preferredaspect, after hydrolyzing, a method of performing aqueous washing, acidwashing, aqueous washing, alkaline washing and aqueous washing in order,a method of performing acid washing, aqueous washing, alkaline washingand aqueous washing in order, a method of performing acid washing andaqueous washing in order, and the like can be included. Each washing maybe repeated plural times.

Acid washing can be performed by adding hydrochloric acid to thesolution including the obtained polythiol composition. The concentrationof hydrochloric acid can be set to from 25% to 36%, and preferably 30%to 36%. When the concentration of hydrochloric acid is lower than 25%,there are cases where clouding occurs in the plastic lens by impuritiesor the like. In addition, the temperature of acid washing can be set tofrom 10° C. to 50° C., preferably from 15° C. to 50° C., more preferablyfrom 20° C. to 50° C., and even more preferably from 30° C. to 45° C.

For aqueous washing, degassed water in which the concentration of oxygenis equal to or less than 7 mg/L can be used.

As a process of producing degassed water, a method of blowing nitrogento remove dissolved oxygen, a method of driving out dissolved oxygen bythe heat treatment, a method of driving out dissolved oxygen by thevacuum degassing, and the like are included, however, the method is notparticularly limited, if the method can make the concentration of oxygenbe equal to or less than 5 mg/L.

In this manner, it is possible to effectively suppress color orturbidity which becomes a problem in the optical material such as theplastic lens.

In addition, alkaline washing can be performed by adding an alkalineaqueous solution and stirring in a range from 20° C. to 50° C. for 10minutes to 3 hours. As an alkaline aqueous solution, aqueous ammonia ispreferable. In addition, the concentration of aqueous ammonia can be setto from 0.1% to 10%, preferably 0.1% to 1%, more preferably 0.1% to0.5%.

Moreover, also in acid washing and alkaline washing, by using water inwhich the concentration of oxygen is equal to or less than 7 mg/L, it ispossible to effectively suppress color or turbidity which becomes aproblem in the optical material such as the plastic lens.

After the step D, by performing a step of removing a solvent, a step ofremoving a low boiling point compound as necessary, a step of filtering,and a step of distilling, it is possible to obtain the polythiolcomposition including 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctaneas a polythiol compound.

The step of removing a solvent is a step of removing an organic solventunder normal pressures or reduced pressure, and the decompression degreeand the temperature are appropriately selected according to the usedsolvent or the like, however, it is preferable that the step beperformed at 100° C. or less, and preferably 85° C. or less, underreduced pressure.

The step of removing a low boiling point compound is a step of removingthe low boiling point compound contained in the target compound undernormal pressures or reduced pressure after the step of removing asolvent, and the decompression degree and the temperature areappropriately selected according to the used solvent or the like,however, it is preferable that the step be performed at equal to orlower than 100° C., and preferably equal to or lower than 85° C., underreduced pressure. In doing so, the step may be performed whileventilating inert gas such as nitrogen gas.

The step of filtering is a step of removing by filtering a solidmaterial such as a salt, and a method of filtering and the like areappropriately selected, however, a filtration under reduced pressure ora pressure filtration using a membrane filter or a cartridge filter andthe like can be used. It is preferable that the step be performed with afilter which the pore size of a filter is equal to or less than 5 μm,and preferably equal to or less than 2 μm.

The step of distilling is a step of purifying the polythiol compound bydistilling, and the decompression degree and the temperature areappropriately selected according to the used solvent or the like,however, it is preferable that the step be performed at equal to orlower than 250° C., and preferably equal to or lower than 200° C., underreduced pressure.

In addition, in order to adjusting the ratio of the peak area of thenitrogen-containing compound (B), a step of reducing thenitrogen-containing compound (B) by purifying by means of acid washingis sometimes employed. In this case, it is necessary to confirm theamount of the nitrogen-containing compound (B) included in the polythiolcomposition and appropriately set the conditions of acid washing so thatthe amount of the nitrogen-containing compound (B) is in thepredetermined range.

It is considered that the ratio of the peak area of thenitrogen-containing compound (B) is multiply determined by a combinationof the conditions over a plurality of steps during synthesizing orpurifying. On the other hand, the producing conditions disclosed in thepresent invention have extremely good repeatability and can provide thepolythiol composition including the nitrogen-containing compound (B) inthe predetermined range.

Moreover, the process of producing of the present embodiment can also beconducted in the air, however, it is preferable that the process ofwhole producing be performed under a nitrogen atmosphere in the light ofcolor.

By such a process of producing, the polythiol composition including thepolythiol compound (A) and the nitrogen-containing compound (B) with thepredetermined range in the present embodiment can be suitably obtained.

Embodiment II

In embodiment II, a case of producing “a polythiol compound which isprimarily comprised of at least one kind selected from the groupconsisting of4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane” is describedas follows. Moreover, description of the same steps as an embodiment Iwill not be repeated.

Hereinafter, each step is described in order.

(Step A)

In the present embodiment, firstly, by 2-mercaptoethanol reacting withan epihalohydrin compound represented by the following formula (1),

It is possible to obtain a diol compound represented by the followingformula (3).

In the formula (1) described above, X is a halogen atom which is afluorine atom, a chlorine atom, a bromine atom, or an iodine atom, andpreferably a chlorine atom.

In the present embodiment, the reaction can be performed in a range from2° C. to 30° C., preferably from 5° C. to 20° C., and more preferablyfrom 5° C. to 15° C. The reaction can be performed for 2 hours to 10hours.

Specifically, the reaction can be performed as follows.

Firstly, epihalohydrin is added dropwise into a solution comprised of2-mercaptoethanol, and water or lower alcohol solution such as methanolor ethanol as necessary, and an aqueous solution of the above base orlower alcohol such as methanol or ethanol solution of the above base. Itis preferable to adjust so that the reaction temperature and thereaction time are in the ranges described above. In the solution towhich epihalohydrin is added dropwise, the used amount of2-mercaptoethanol is equal to or more than 0.5 mol and equal to or lessthan 3 mol, preferably equal to or more than 0.7 mol and equal to orless than 2 mol, and more preferably equal to or more than 0.9 mol andequal to or less than 1.1 mol, with respect to 1 mol of epihalohydrin.In addition, the base described above of the catalyst quantity is used,and in a case of a monovalent base, the used amount of the basedescribed above is preferably equal to or more than 0.001 mol and equalto or less than 0.1 mol, with respect to 1 mol of epihalohydrin. In acase of a bivalent base, the half amount of the used amount of amonovalent base is preferable. The base can be used as an aqueoussolution, an alcohol solution, or the like, and in a case of using as asolution, the concentration of the base can be appropriately selected.By epihalohydrin being added dropwise into the solution described above,diol represented by the formula (3) is obtained.

(Step B)

Next, by the diol compound represented by the formula (3) describedabove reacting with sodium sulphide, a tetraol compound represented bythe following formula (4) can be obtained.

In the present embodiment, the reaction can be performed in a range from10° C. to 50° C., and preferably from 20° C. to 40° C. The reaction canbe performed for 1 hour to 10 hours.

Specifically, the reaction can be performed as follows.

Sodium sulphide aqueous solution is added dropwise or the sodiumsulphide solid is charged into the reaction solution including the diolcompound after the reaction described above. It is preferable to adjustso that the reaction temperature and the reaction time are in the rangesdescribed above. Sodium sulphide can be used with the amount from 0.4mol to 0.6 mol, preferably 0.45 mol to 0.57 mol, more preferably 0.48mol to 0.55 mol, with respect to 1 mol of the diol compound.

(Step C)

Next, by the tetraol compound obtained in the step B and represented bythe formula (4) reacting with thiourea in the presence of hydrogenchloride to obtain the isothiuronium salt.

Specifically, thiourea which is equal to or more than 3 mol, preferablyequal to or more than 3 mol and equal to or less than 6 mol, and morepreferably equal to or more than 4.6 mol and equal to or less than 5.0mol, with respect to 1 mol of the tetraol compound is added to thetetraol compound to react. The reaction is performed in the presence ofhydrogen chloride which is equal to or more than 3.0 mol, and preferablyequal to or more than 3 mol and equal to or less than 12 mol, withrespect to 1 mol of the tetraol compound in a range from roomtemperature to the reflux temperature, and preferably at the temperaturefrom 90° C. to 120° C., for approximately 1 hour to 10 hours. By thereaction of the tetraol compound and thiourea, the isothiuronium saltcompound is formed. By using hydrogen chloride, it is possible to obtainthe sufficient reaction speed, furthermore, control the coloration of aproduct. As hydrogen chloride, a hydrochloric acid aqueous solution andhydrogen chloride gas can be used.

(Step D)

Aqueous ammonia is added into the reaction solution including theisothiuronium salt obtained in the step C to hydrolyze the isothiuroniumsalt and the polythiol composition is obtained.

In the present embodiment, as a polythiol compound, it is possible toobtain the polythiol composition including the polythiol compound whichis primarily comprised of at least one kind selected from the groupconsisting of

-   4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane    represented by the following formula (6),-   4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane    represented by the following formula (7), and-   5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane    represented by the following formula (8).

Specifically, while the reaction solution including the isothiuroniumsalt is maintained in a range of the temperature from 20° C. to 60° C.,preferably from 25° C. to 55° C., and more preferably from 25° C. to 50°C., aqueous ammonia is added into the reaction solution for equal to orshorter than 80 minutes, preferably equal to or shorter than 70 minutes,more preferably from 20 minutes to 60 minutes, and even more preferablyfrom 20 minutes to 30 minutes. The time of adding aqueous ammonia ispreferably shorter, however, the time is set to within the timedescribed above, considering the equipment capacity such as coolability,or the like.

Before adding aqueous ammonia, an organic solvent is preferably added.By adding the organic solvent, it is possible to suppress to produce aby-product. The additive amount of the organic solvent is appropriatelyselected according to the classification of the solvent, or the like,however, it is possible to add with the amount which is from 0.1 timesto 3.0 times, and preferably from 0.2 times to 2.0 times, with respectto the thiuronium salt reaction solution. As an organic solvent,toluene, xylene, chlorobenzene, dichlorobenzene, and the like areincluded. Toluene is preferable, from the viewpoint of the effectdescribed above.

Aqueous ammonia can be added within the addition time described above sothat ammonia (NH₃) is equal to or more than 1 mol, preferably equal toor more than 1 mol and equal to or less than 3 mol, and more preferablyequal to or more than 1.1 mol and equal to or less than 2 mol, with 1mol of the used amount of hydrogen chloride described above. Theconcentration of aqueous ammonia can be set to from 10% to 25%. Inaddition, ammonia gas can also be used instead of aqueous ammonia. In acase where ammonia gas is added in place of all or part of aqueousammonia, it is possible to perform in the same conditions (the usedamount, the addition time, the addition temperature) as aqueous ammonia.

In the present embodiment, ammonia (NH₃) is added so that the additionrate is equal to or more than 1.25 mol %/minute, preferably equal to ormore than 1.25 mol %/minute and equal to or less than 3.75 mol %/minute,and more preferably equal to or more than 1.38 mol %/minute and equal toor less than 2.5 mol %/minute, with respect to 1 mol of hydrogenchloride. In the step, it is not necessary to continuously add with therate described above, and the average addition rate in the addition timedescribed above has only to be included in the range.

And, after aqueous ammonia is added, a hydrolysis reaction is continuedto be performed in a range from room temperature to the refluxtemperature, and preferably at the temperature from 30° C. to 80° C.,for approximately 1 hour to 8 hours.

(Step E)

In the present embodiment, the polythiol composition obtained in thestep D is purified. The step E in the present embodiment can beperformed in the same way as embodiment I.

In addition, the step after the step E can also be performed in the sameway as Embodiment I.

By such a process of producing, the polythiol composition including thepolythiol compound (A) and the nitrogen-containing compound (B) in thepredetermined range in the present embodiment can be suitably obtained.

As described above, in the present embodiment, specifically, descriptionof the process of producing the polythiol composition including twotypes of polythiol compound as the polythiol compound (A) has been givenas an example, however, other method can be employed if the ratio of thepeak area of the nitrogen-containing compound (B) can be set to thepredetermined range.

In addition, for even polythiol compound except the two types selectedfrom the exemplified polythiol compounds described above, byappropriately changing the producing conditions, the ratio of the peakarea of the nitrogen-containing compound (B) can be set to thepredetermined range.

<Polymerizable Composition for Optical Material>

The polymerizable composition for the optical material in the presentembodiment includes the polythiol composition for the optical materialwhich is obtained by the method described above and polyiso(thio)cyanatecompound.

The polyiso(thio)cyanate compound is not particularly limited as long asthe polyiso(thio)cyanate compound is a compound having at least two ormore iso(thio)cyanate groups in one molecule. However, specifically, thepolyiso(thio)cyanate includes an aliphatic polyisocyanate compound suchas hexamethylene diisocyanate, 1,5-pentane diisocyanate,2,2-dimethylpentane diisocyanate, 2,2,4-trimethylhexane diisocyanate,butene diisocyanate, 1,3-butadiene-1,4-diisocyanate,2,4,4-trimethylhexamethylene diisocyanate, 1,6,11-undecanetriisocyanate, 1,3,6-hexamethylene triisocyanate,1,8-diisocyanato-4-isocyanatomethyloctane,bis(isocyanatoethyl)carbonate, bis(isocyanatoethyl)ether, lysinediisocyanatomethyl ester, or lysine triisocyanate; an alicyclicpolyisocyanate compound such as isophorone diisocyanate,bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate,cyclohexane diisocyanate, methylcyclohexane diisocyanate,dicyclohexyldimethylmethane isocyanate,2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane,2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane,3,8-bis(isocyanatomethyl)tricyclodecane,3,9-bis(isocyanatomethyl)tricyclodecane,4,8-bis(isocyanatomethyl)tricyclodecane,4,9-bis(isocyanatomethyl)tricyclodecane,bis(4-isocyanatocyclohexyl)methane,1,3-bis(isocyanatomethyl)cyclohexane, or1,4-bis(isocyanatomethyl)cyclohexane;

a polyisocyanate compound having an aromatic ring compound such as1,2-diisocyanatobenzene, 1,3-diisocyanatobenzene,1,4-diisocyanatobenzene, tolylene diisocyanate, 2,4-diisocyanatotoluene,2,6-diisocyanatotoluene, ethylphenylene diisocyanate, isopropylphenylenediisocyanate, dimethylphenylene diisocyanate, diethylphenylenediisocyanate, diisopropylphenylene diisocyanate, trimethylbenzenetriisocyanate, benzene triisocyanate, biphenyl diisocyanate, toluidinediisocyanate, 4,4′-methylenebis(phenyl isocyanate),4,4′-methylenebis(2-methylphenyl isocyanate),bibenzyl-4,4′-diisocyanate, bis(isocyanatophenyl)ethylene,bis(isocyanatemethyl)benzene, m-xylylene diisocyanate,bis(isocyanatoethyl)benzene, bis(isocyanatopropyl)benzene,α,α,α′,α′-tetramethylxylylene diisocyanate, bis(isocyanatobutyl)benzene,bis(isocyanatomethyl)naphthalene, bis(isocyanatomethylphenyl)ether,bis(isocyanatoethyl)phthalate, or 2,5-di(isocyanatomethyl)furan;a sulfur-containing aliphatic polyisocyanate compound such asbis(isocyanatomethyl)sulfide, bis(isocyanatoethyl)sulfide,bis(isocyanatopropyl)sulfide, bis(isocyanatohexyl)sulfide,bis(isocyanatomethyl)sulfone, bis(isocyanatomethyl)disulfide,bis(isocyanatoethyl)disulfide, bis(isocyanatopropyl)disulfide,bis(isocyanatomethylthio)methane, bis(isocyanatoethylthio)methane,bis(isocyanatomethylthio)ethane, bis(isocyanatoethylthio)ethane,1,5-diisocyanato-2-isocyanatomethyl-3-thiapentane,1,2,3-tris(isocyanatomethylthio)propane,1,2,3-tris(isocyanatoethylthio)propane, 3,5-dithia-1,2,6,7-heptanetetraisocyanate, 2,6-diisocyanatomethyl-3,5-dithia-1,7-heptane diisocyanate,2,5-diisocyanate methyl thiophene, or4-isocyanatoethylthio-2,6-dithia-1,8-octane diisocyanate;an aromatic sulfide-based polyisocyanate compound such as2-isocyanatophenyl-4-isocyanatophenyl sulfide,bis(4-isocyanatophenyl)sulfide, or bis(4-isocyanatomethylphenyl)sulfide;an aromatic disulfide-based polyisocyanate compound such asbis(4-isocyanatophenyl)disulfide,bis(2-methyl-5-isocyanatophenyl)disulfide,bis(3-methyl-5-isocyanatophenyl)disulfide,bis(3-methyl-6-isocyanatophenyl)disulfide,bis(4-methyl-5-isocyanatophenyl)disulfide, orbis(4-methoxy-3-isocyanatophenyl)disulfide;a sulfur-containing alicyclic polyisocyanate compound such as2,5-diisocyanato tetrahydrothiophene, 2,5-diisocyanatomethyltetrahydrothiophene, 3,4-diisocyanatomethyl tetrahydrothiophene,2,5-diisocyanato-1,4-dithiane, 2,5-diisocyanatomethyl-1,4-dithiane,4,5-diisocyanato-1,3-dithiolane,4,5-bis(isocyanatomethyl)-1,3-dithiolane, or4,5-diisocyanatomethyl-2-methyl-1,3-dithiolane;an aliphatic polyisothiocyanate compound such as1,2-diisothiocyanatoethane or 1,6-diisothiocyanatohexane;an alicyclic polyisothiocyanate compound such as cyclohexanediisothiocyanate;an aromatic polyisothiocyanate compound such as 1,2-diisothiocyanatobenzene, 1,3-diisothiocyanato benzene, 1,4-diisothiocyanato benzene,2,4-diisothiocyanato toluene, 2,5-diisothiocyanato-m-xylene,4,4′-methylenebis(phenyl isothiocyanate),4,4′-methylenebis(2-methylphenyl isothiocyanate),4,4-methylenebis(3-methylphenyl isothiocyanate), 4,4′-diisothiocyanatobenzophenone, 4,4′-diisothiocyanato-3,3′-dimethyl benzophenone, orbis(4-isothiocyanatophenyl)ether;furthermore, a carbonyl polyisothiocyanate compound such as 1,3-benzenedicarbonyl diisothiocyanate, 1,4-benzene dicarbonyl diisothiocyanate, or(2,2-pyridine)-4,4-dicarbonyl diisothiocyanate;a sulfur-containing aliphatic polyisothiocyanate compound such asthiobis(3-isothiocyanatopropane), thiobis(2-isothiocyanatoethane), ordithiobis(2-isothiocyanatoethane);a sulfur-containing aromatic polyisothiocyanate compound such as1-isothiocyanato-4-[(2-isothiocyanato)sulfonyl]benzene,thiobis(4-isothiocyanatobenzene), sulfonyl(4-isothiocyanatobenzene), ordithiobis(4-isothiocyanatobenzene);a sulfur-containing alicyclic polyisothiocyanate compound such as2,5-diisothiocyanatothiophene, or 2,5-diisothiocyanato-1,4-dithiane;a compound having an isocyanato group and an isothiocyanato group suchas 1-isocyanato-6-isothiocyanatohexane,1-isocyanato-4-isothiocyanatocyclohexane,1-isocyanato-4-isothiocyanatobenzene,4-methyl-3-isocyanato-1-isothiocyanatobenzene,2-isocyanato-4,6-diisothiocyanate-1,3,5-triazine,4-isocyanatophenyl-4-isothiocyanatophenyl sulfide, or2-isocyanatoethyl-2-isothiocyanatoethyl disulfide, and the like.

A polyiso(thio)cyanate compound preferably includes an aliphatic-basedpolyisocyanate compound such as hexamethylene diisocyanate,1,5-pentanediisocyanate, isophorone diisocyanate,bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate,2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane,2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane,bis(4-isocyanatocyclohexyl)methane,1,3-bis(isocyanatomethyl)cyclohexane, or1,4-bis(isocyanatomethyl)cyclohexane;

a polyisocyanate compound having an aromatic ring compound such asbis(isocyanatomethyl)benzene, m-xylylene diisocyanate,1,3-diisocyanatobenzene, tolylene diisocyanate, 2,4-diisocyanatotoluene,2,6-diisocyanatotoluene, 4,4′-methylenebis(phenylisocyanate).

In addition, it is possible to use a halogen substitution thereof suchas a chlorine substitution or a bromine substitution, an alkylsubstitution thereof, an alkoxy substitution thereof, a nitrosubstitution thereof, a prepolymer type modified product withpolyalcohol, a carbodiimide modified product, a urea modified product, aburet modified product, a reaction product of dimerization ortrimerization, and the like. The compounds may be used alone or in acombination of two types or more.

As a polythiol compound used in the polymerizable composition for theoptical material, in addition to the polythiol compound for the opticalmaterial which is obtained by the method described above, otherpolythiol compound for the optical material can be used.

Other polythiol compound for the optical material preferably includes analiphatic polythiol compound such as methane dithiol, 1,2-ethanedithiol,1,2,3-propanetrithiol, pentaerythritol tetrakis(2-mercaptoacetate),pentaerythritol tetrakis(3-mercaptopropionate),bis(mercaptoethyl)sulfide, 2,5-dimercaptomethyl-1,4-dithiane,tetrakis(mercaptomethylthio methyl)methane, tetrakis(2-mercaptoethylthiomethyl)methane, tetrakis(3-mercaptopropylthio methyl)methane,bis(2,3-dimercaptopropyl)sulfide, 2,5-dimercaptomethyl-1,4-dithiane,2,5-dimercapto-1,4-dithiane,2,5-dimercaptomethyl-2,5-dimethyl-1,4-dithiane,1,1,3,3-tetrakis(mercaptomethylthio)propane,1,1,2,2-tetrakis(mercaptomethylthio)ethane, or4,6-bis(mercaptomethylthio)-1,3-dithiane.

The usage ratio of the polythiol compound and the polyiso(thio)cyanatecompound is not particularly limited, however, the molar ratio isusually within a range of a SH group/a NCO group=0.5 to 3.0, within arange of preferably 0.6 to 2.0, and more preferably 0.8 to 1.3. If theusage ratio is within the range described above, it becomes possible tosatisfy a nice balance of various kinds of performance such as therefractive index or the heat resistance demanded as the optical materialsuch as the plastic lens and the transparent material.

For the purpose to improve various properties, the operability, thepolymerization reactivity, or the like of the polythiourethane-basedresin of the present invention, other substances may be added, inaddition to the polythiol compound and the iso(thio)cyanate compoundwhich form an urethane resin. For example, at least one kind of anactive hydrogen compound which is typified by amine or the like, acarbonate compound, an ester compound, a metal, a metallic oxide, anorganic metal compound, an inorganic substance, or the like may beadded, in addition to a urethane forming material.

In addition, in accordance with the purpose, various kinds of substancessuch as a chain extender, a crosslinking agent, a light stabilizer, anultraviolet absorber, an antioxidizing agent, an oil color, a filler, ora mold release agent may be added in the same way as a well-knownforming process. In order to adjust the desired reaction rate, awell-known reaction catalyst used in producing a thiocarbamic acids-alkyl ester or a polythiourethane-based resin may be appropriatelyadded. As a reaction catalyst, a well-known reaction catalyst used inproducing a thiocarbamic acid S-alkyl ester or a polythiourethane-basedresin can be appropriately added.

A reaction catalyst includes dialkyltin halides such as dibutyltindichloride, or dimethyltin dichloride, dialkyltin dicarboxylates such asdimethyltin diacetate, dibutyltin dioctanoate, or dibutyltin dilaurate,dialkyltin dialkoxides such as dibutyltin dibutoxide, dioctyltindibutoxide, or dialkyltin dithioalkoxides such as dibutyltindi(thiobutoxide), dialkyltin oxides such as di(2-ethylhexyl)tin oxide,dioctyltin oxide, or bis(butoxy dibutyltin)oxide, dialkyltin sulfidessuch as dibutyltin sulfide are included. Dialkyltin halides such asdibutyltin dichloride, dimethyltin dichloride, as a preferred example.

Furthermore, as a purpose of modifying a resin, a resin modifying agentsuch as a hydroxyl compound, an epoxy compound, an episulphide compound,an organic acid and an anhydride thereof, an olefin compound including a(metha) acrylate compound or the like may be added. Here, a resinmodifying agent is a compound which adjusts or improves properties of amaterial comprised of a thiourethane-based resin such as the refractiveindex, the Abbe number, the heat resistance and the specific gravity,and the mechanical strength thereof such as the impact resistance, orthe like.

In addition, the polymerizable composition for the optical material ofthe present embodiment can include a blueing agent, as necessary. Theblueing agent has an absorption band in a wavelength range fromorange-colored to yellow-colored in a visible light region and has afunction of adjusting color of an optical material comprised of a resin.More specifically, the blueing agent includes a substance showing fromblue-colored to purple-colored.

The blueing agent used in the polymerizable composition for the opticalmaterial of the present embodiment is not particularly limited,specifically, a dye, a fluorescent brightening agent, a fluorescentpigment, an inorganic pigment and the like are included, however, fromamong the substances which can be used as a blueing agent, the blueingagent is appropriately selected, according to physical properties whichare required for the optical components, resin color, or the like. Theblueing agents may be respectively used alone or in a combination two ormore kinds.

Among the blueing agents, a dye is preferable, from the viewpoint of thesolubility to the polymerizable composition and the viewpoint of thetransparency of the optical material which is obtained.

From the viewpoint of the absorption wavelength, it is preferred that adye in which the maximum absorption wavelength is equal to or more than520 nm and equal to or less than 600 nm is used. It is more preferredthat a dye in which the maximum absorption wavelength is equal to ormore than 540 nm and equal to or less than 580 nm is used.

In addition, an anthraquinone-based dye is preferable, from theviewpoint of the structure of the compound.

A method of adding the blueing agent is not particularly limited, and itis desired to add to a monomer system in advance. As method, variouskinds of methods such as a method of being dissolved in a monomer or amethod in which a master solution containing the high concentration ofthe blueing agent is prepared and the master solution is diluted by amonomer or other additive agent which is used to be added can beemployed.

The polymerizable composition for the optical material of the presentembodiment is obtained as a mixed liquid, specifically, by mixing thepolythiol composition obtained by the process of producing describedabove and the polyiso(thio)cyanate compound, furthermore othercomponents as necessary. The mixed liquid is put into a mold and isusually, gradually heated from a low temperature to a high temperatureto be polymerized after degassing by an appropriate method as necessary.

In this manner, a molded product comprised of the polythiourethane-basedresin obtained by curing the polymerizable composition of the presentembodiment has characteristics which are the high refractive index, thelow dispersion, excellent heat resistance and durability, light weigh,and excellent impact resistance, furthermore, color is favorable and itis suitable as the optical material such as a spectacle lens, a cameralens and the transparent material element.

In addition, the plastic lens obtained by using thepolythiourethane-based resin of the present embodiment may be subjectedto a physical or chemical treatment such as the surface polishing, theantistatic treatment, the hard coat treatment, the antireflection coattreatment, the dyeing treatment, the dimming treatment as necessary, inorder to perform an improvement of anti-reflection, imparting highhardness, enhancing abrasive resistance, enhancing chemical resistance,imparting antifog properties, imparting fashionability, or the like.

EXAMPLES

Hereinafter, more detailed description will be given of the presentinvention according to Examples, however, the present invention is notlimited thereto.

Moreover, in the following Examples, properties were measured by thefollowing methods of measurement.

-   -   Specific gravity: measured in conformity to JIS K 0061.    -   APHA: APHA is a method of displaying color and determined by        using a standard solution which was prepared by dissolving a        reagent of platinum and cobalt and comparing the standard        solution diluted solution having the concentration equal to the        color of samples, the “frequency” was set to the measured value.    -   The amount of water: A monomer was dissolved in toluene, and the        water measurement was conducted by Karl Fischer Moisture        Titrate.    -   Viscosity: It was measured in accordance with JIS K 7117.    -   Refractive index: It was measured at 20° C. by RA-600 digital        refractometer manufactured by KYOTO ELECTRONICS MANUFACTURING        CO., LTD.    -   Ammonium content: A monomer was dissolved in chloroform,        extracted by water and measured by an ion chromatography.    -   Acid content: A monomer was dissolved in a solvent, calculated        as the HCl content by titrating by a methanol solution of KOH.    -   Loss degree of transparency of resin: A flat plate of 9 mm was        produced with the producing conditions of the plastic lenses of        Examples to measure by a loss degree of transparency measuring        apparatus (manufactured by HAYASHI WATCH-WORKS: LUMINAR ACE        LA-150SE).    -   Resin YI: It is a yellow index in the evaluation of color. YI is        measured by a color-difference meter. A flat plate of 9 mm was        produced with the producing conditions of the plastic lenses of        Examples to measure a YI value using a color-difference meter        (CR-400) manufactured by KONICA MINOLTA, INC.    -   Striation: The lens was produced with the producing conditions        of the plastic lenses of Examples and visually observed under a        high-pressure mercury lamp, and the lens in which a stripe-like        pattern was not observed was O and the lens in which a        stripe-like pattern was observed was X.

In addition, dissolved oxygen was turned out of water by blowinghydrogen into water to obtain degassed water which is 2 ppm of theconcentration of dissolved oxygen.

Example A-1 Synthesis of Polythiol Composition which is PrimarilyComprised of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane

124.6 parts by weight of 2-mercaptoethanol and 18.3 parts by weight ofdegassed water (the concentration of dissolved oxygen is 2 ppm) werecharged into a reaction vessel. After 101.5 parts by weight of 32% byweigh of sodium hydroxide aqueous solution was added dropwise andcharged from 12° C. to 35° C. over 40 minutes, 73.6 parts by weight ofepichlorohydrin was added dropwise and charged from 29° C. to 36° C.over 4.5 hours, and continuously, stirring was performed for 40 minutes.From an NMR data, the production of1,3-bis(2-hydroxyethylthio)-2-propanol was confirmed.

331.5 parts by weight of 35.5% hydrochloric acid was charged, andsubsequently, 183.8 parts by weight of the purity of 99.90% of thioureawas charged and stirred at 110° C. for 3 hours under reflux to convertinto a thiuronium salt. After cooling to 45° C., 320.5 parts by weightof toluene was added and cooled to 31° C., 243.1 parts by weight of 25%by weight of ammonia aqueous solution was charged from 31° C. to 41° C.over 44 minutes and stirred from 54° C. to 62° C. for 3 hours, and atoluene solution of the polythiol composition which is primarilycomprised of 4-mercaptomethyl-1, 8-dimercapto-3, 6-dithiaoctane wasobtained. 162.8 parts by weight of 35.5% hydrochloric acid was addedinto the toluene solution and acid washing was performed from 35° C. to43° C. for 1 hour. 174.1 parts by weight of degassed water (theconcentration of dissolved oxygen is 2 ppm) was added and washing whichwas performed from 35° C. to 45° C. for 30 minutes was conducted twice.162.1 parts by weight of 0.1% aqueous ammonia was added to wash for 30minutes. 174.2 parts by weight of degassed water was added and washingwhich was performed from 35° C. to 45° C. for 30 minutes was conductedtwice. After toluene and trace water were removed under heating andreduced pressure, filtration under reduced pressure was performed byPTFE type membrane filter of 1.2 μm to obtain 205.0 parts by weight of apolythiol composition which is primarily comprised of4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane. Physical properties ofthe obtained polythiol composition are shown in Table-1.

The results of an elementary analysis and a NMR analysis of4-mercaptomethyl-1, 8-dimercapto-3,6-dithiaoctane are shown.

Elementary analysis (as C₇H₁₆S₅)

CHS analysis value 32.12 6.19 61.69 Calculated value 32.27 6.19 61.53 ¹HNMR (CDCl₃)

δ_(ppm)=1.74 to 1.91 (3H, m, SH)

2.70 to 3.00 (13H, m, CH)

(Purification and Structure Confirmation)

By a silica gel column chromatography (toluene-methanol, stepwisemethod) was repeatedly performed, a nitrogen-containing compound(referred to as B-1) was fractionated and purified from the polythiolcomposition which is primarily comprised of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane.

From the results of instrumental analysis, it was identified that thenitrogen-containing compound (B-1) had a structure in which one of amercapto group of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane wasreplaced with a group represented by the following formula (a),furthermore other one of a mercapto group was replaced with a hydroxylgroup. In the following formula (a), * represents an atomic bonding.

(1) Mass spectrum

FAB-MS: m/z370 (M⁺) (Matrix m-NBA)

(2) IR (Universal ATR method):

3300 cm⁻¹: NH stretching, 2541 cm⁻¹: SH stretching, 1606 cm⁻¹: C═Nstretching, 1520 cm⁻¹: NH vending.

(3)¹H-NMR (DMSO-d₆):

δ ppm 2.3-2.9 (11H (—CH₂—, SH)), 3.1-3.45 (3H (—CH—, CH₂OH)), 6.6-6.8(6H (NH₂)).

(4)¹³C-NMR (DMSO-d₆):

δ ppm 24-40 (CH₂), 46-48 (CH), 70.3 (C—OH (C adjacent to 0)), 166.5,178.1 (—C—N— (melamine skeleton)).

The ratio of the peak area of the nitrogen-containing compound (B-1) to4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane (referred to as apolythiol compound (A-1)) was determined in the following manner.

1. Measurement Conditions of High Performance Liquid Chromatography

Column: YMC-Pack ODS-A A-312 (S5Φ6 mm×150 mm)

Mobile phase: acetonitrile/0.01 mol-potassium dihydrogen phosphateaqueous solution=60/40 (vol/vol)

Column temperature: 40° C.

Flow rate: 1.0 ml/min

Detector: UV detector, wavelength 230 nm

Preparation of measurement solution: 160 mg of a sample is dissolved andmixed in 10 ml of acetonitrile.

Injection volume: 2 μL

2. Ratio of the Peak Area of Nitrogen-Containing Compound (B-1)

In the polythiol composition which was produced in Example A-1, theratio of the peak area of the nitrogen-containing compound (B-1) to thepolythiol compound (A-1) was calculated using the following expression.Expression: {[peak area of nitrogen-containing compound (B-1)]/[peakarea of polythiol compound (A-1)]}×100

The result calculated using the expression for computation describedabove was 0.21.

Moreover, the retention times of the polythiol compound (A-1) and thenitrogen-containing compound (B-1) were as follows. A chart of highperformance liquid chromatography is shown in FIG. 1.

Polythiol compound (A-1): From 12.0 minutes to 13.5 minutes.

Nitrogen-containing compound (B-1): From 4.3 minutes to 5.6 minutes.

(Manufacturing of Plastic Lens)

52 parts by weight of m-xylylene diisocyanate, 0.015 parts by weight ofdibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by CHEMICAL CO., LTD.; ultraviolet absorbing agent) weremixed and dissolved at 20° C. 48 parts by weight of the obtainedpolythiol composition which is primarily comprised of the polythiolcompound (A-1) was charged and mixed to set to a mixed homogeneousliquid. After the homogeneous liquid was degassed at 600 Pa for 1 hour,the homogeneous liquid was put into a mold die consisting of a glassmold and a tape after filtrating using a Teflon (registered trademark)filter of 1 μm. The mold die was put into an oven, gradually heated upfrom 10° C. to 120° C., and polymerized for 20 hours. After thepolymerization was finished, the mold die was taken out from the oven toobtain a resin by releasing from the mold die. The obtained resin wasfurther annealed at 120° C. for 3 hours. Physical properties of theobtained plastic lens are shown in Table-1.

Examples A-2 to A-10

The polythiol composition which is primarily comprised of the polythiolcompound (A-1) in the same way as Example A-1 except setting to theproducing conditions described in Table-1 was produced and the plasticlens was manufactured. The results are shown in Table-1.

Example B-1 Synthesis of Polythiol Composition which is PrimarilyComprised of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane

124.6 parts by weight of 2-mercaptoethanol and 18.3 parts by weight ofdegassed water (the concentration of dissolved oxygen is 2 ppm) werecharged into a reaction vessel. After 101.5 parts by weight of 32% byweigh of sodium hydroxide aqueous solution was added dropwise andcharged from 12° C. to 35° C. over 40 minutes, 73.6 parts by weight ofepichlorohydrin was added dropwise and charged from 28° C. to 36° C.over 4.5 hours, and continuously, stirring was performed for 40 minutes.From NMR data, the production of 1, 3-bis(2-hydroxyethylthio)-2-propanolwas confirmed.

Next, 183.7 parts by weight of the purity of 99.90% of thiourea wascharged, 108.6 parts by weight of the purity of 90.7% of hydrochloricacid gas was blown and stirred at 110° C. for 3 hours under reflux toconvert into a thiuronium salt. After cooling to 45° C., 320.5 parts byweight of toluene was added and cooled to 31° C., 216.7 parts by weightof 25% by weight of aqueous ammonia solution was charged from 31° C. to40° C. over 29 minutes and matured from 54° C. to 63° C. for 3 hours,and a toluene solution of the polythiol composition which is primarilycomprised of 4-mercaptomethyl-1, 8-dimercapto-3, 6-dithiaoctane wasobtained. 162.9 parts by weight of 35.5% hydrochloric acid was addedinto the toluene solution and acid washing was performed from 34° C. to43° C. for 1 hour. 174.2 parts by weight of degassed water (theconcentration of dissolved oxygen is 2 ppm) was added and washing whichwas performed from 35° C. to 45° C. for 30 minutes was conducted twice.162.8 parts by weight of 0.1% aqueous ammonia was added to wash for 30minutes. 174.2 parts by weight of degassed water (the concentration ofdissolved oxygen is 2 ppm) was added and washing which was performedfrom 34° C. to 43° C. for 30 minutes was conducted twice. After tolueneand trace water were removed under heating and reduced pressure,filtration under reduced pressure was performed by PTFE type membranefilter of 1.2 μm to obtain 205.0 parts by weight of polythiolcomposition which is primarily comprised of4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane (a polythiol compound(A-1)). Physical properties of the obtained polythiol composition areshown in Table-1.

The identification of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctanewas performed in the same way as Example A-1 and the same results wereobtained.

(Purification and Structure Confirmation)

By a silica gel column chromatography (toluene-methanol, stepwisemethod) was repeatedly performed, the nitrogen-containing compound (B-1)was fractionated and purified from the polythiol composition which isprimarily comprised of polythiol compound (A-1).

From the results of instrumental analysis, it was identified that thenitrogen-containing compound (B-1) had a structure in which one of amercapto group of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane wasreplaced with a group represented by the following formula (a),furthermore other one of a mercapto group was replaced with a hydroxylgroup. In the following formula (a), * represents an atomic bonding.

(1) Mass spectrum

FAB-MS: m/z370 (M⁺) (Matrix m-NBA)

(2) IR (Universal ATR method):

3300 cm⁻¹: NH stretching, 2541 cm⁻¹: SH stretching, 1606 cm⁻¹: C═Nstretching, 1520 cm⁻¹: NH vending.

(3)¹H-NMR (DMSO-d₆):

δ ppm 2.3-2.9 (11H (—CH₂—, SH)), 3.1-3.45 (3H (—CH—, CH₂OH)), 6.6-6.8(6H (NH₂)).

(4)¹³C-NMR (DMSO-d₆):

δ ppm 24-40 (CH₂), 46-48 (CH), 70.3 (C—OH (C adjacent to 0)), 166.5,178.1 (—C—N— (melamine skeleton)).

The ratio of the peak area of the nitrogen-containing compound (B-1) to4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane (referred to as apolythiol compound (A-1)) was determined by performing in the same wayas Example A-1.

(Manufacturing Plastic Lens)

52 parts by weight of m-xylylene diisocyanate, 0.015 parts by weight ofdibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by KYODO CHEMICAL CO., LTD.; ultraviolet absorbing agent)were mixed and dissolved at 20° C. 48 parts by weight of the polythiolcomposition which is primarily comprised of the obtained polythiolcompound (A-1) was charged and mixed to set to a mixed homogeneousliquid. After the homogeneous liquid was degassed at 600 Pa for 1 hour,the homogeneous liquid was put into a mold die consisting of a glassmold and a tape after filtrating using a Teflon (registered trademark)filter of 1 μm. The mold die was put into an oven, gradually heated upfrom 10° C. to 120° C., and polymerized for 20 hours. After thepolymerization was finished, the mold die was taken out from the oven toobtain a resin by releasing from the mold die. The obtained resin wasfurther annealed at 120° C. for 3 hours. Physical properties of theobtained lens are shown in Table-1.

Examples B-2 to B-10

The polythiol composition which is primarily comprised of the polythiolcompound (A-1) in the same way as Example B-1 except setting to theproducing conditions described in Table-1 was produced and the plasticlens was manufactured. The results are shown in Table-1.

TABLE 1 Condi- tion I Condition III Analysis value of monomer AddingCondition II Acid Ratio Evaluation of resin drop- Charg- wash- of peakloss de- wise ing Charg- Acid ing Spe- Re- area of gree of temper-temper- ing concen- temper- cific Acid- Wa- Vis- frac- nitrogen- Col-trans- ature ature time tration ature Col- Grav- ity ter cosity tive NH₄containing or parency Stria- ° C. ° C. Minute % ° C. or ity ppm ppm mPa· s index ppm compound YI % tion Example 29-36 31-41 44 35.5 35-43 101.257 10 70 32 1.6310 0.02 0.21 4.2 15 ∘ A-1 Example 28-39 31-41 52 35.534-40 10 1.256 10 30 33 1.6308 0.01 0.20 4.3 18 ∘ A-2 Example 29-3931-41 42 35.5 34-43 10 1.256 12 50 34 1.6308 0.02 0.18 4.3 18 ∘ A-3Example 28-36 31-41 56 35.5 35-44 10 1.257 11 60 33 1.6309 0.05 0.20 4.318 ∘ A-4 Example 29-38 31-40 57 35.5 35-44 10 1.256 12 120 33 1.63080.05 0.26 4.0 17 ∘ A-5 Example 29-32 31-42 53 35.5 34-43 10 1.255 13 8033 1.6310 0.06 0.19 4.0 18 ∘ A-6 Example 29-41 31-42 37 35.5 35-44 101.256 12 110 33 1.6309 0.04 0.24 3.9 17 ∘ A-7 Example 29-37 31-41 5535.5 34-44 10 1.257 7 20 33 1.6312 0.02 0.17 4.2 17 ∘ A-8 Example 28-4031-40 47 30 34-44 10 1.257 8 20 33 1.6312 0.02 0.17 4.2 17 ∘ A-9 Example28-41 31-41 36 30 35-43 10 1.257 8 20 33 1.6313 0.03 0.20 4.4 18 ∘ A-10Example 28-36 31-40 29 35.5 34-43 10 1.256 14 160 33 1.6312 0.04 0.264.4 17 ∘ B-1 Example 29-41 31-40 37 35.5 35-43 10 1.256 20 50 33 1.63150.01 0.29 4.5 18 ∘ B-2 Example 28-37 31-40 35 35.5 35-43 10 1.256 19 2033 1.6311 0.02 0.28 4.3 17 ∘ B-3 Example 28-39 31-39 38 35.5 35-43 101.256 19 70 33 1.6309 0.02 0.31 4.2 18 ∘ B-4 Example 28-40 31-39 37 35.535-43 10 1.256 19 60 33 1.6306 0.01 0.33 4.3 19 ∘ B-5 Example 27-4031-40 31 35.5 35-43 10 1.256 16 50 33 1.6309 0.01 0.29 4.3 18 ∘ B-6Example 25-36 31-40 33 35.5 35-42 10 1.256 15 50 33 1.6309 0.04 0.29 4.218 ∘ B-7 Example 29-38 31-39 32 35.5 35-42 10 1.256 17 60 33 1.6309 0.040.26 4.3 18 ∘ B-8 Example 29-40 31-39 21 30 35-42 10 1.256 16 20 331.6312 0.02 0.30 4.3 18 ∘ B-9 Example 29-39 31-38 38 30 35-43 10 1.25616 20 33 1.6313 0.01 0.28 4.3 19 ∘ B-10 Condition I: Conditions ofreacting 2-mercaptoethanol with epichlorohydrin. Condition II:Conditions of charging an ammonia aqueous solution in a hydrolysisreaction. Condition III: Conditions of hydrochloric acid washing. Ratioof peak area of nitrogen-containing compound: Expression {[peak area ofnitrogen-containing compound (B-1)]/[peak area of polythiol compound(A-1)]} × 100

Examples I-1 to 1-4, Comparative Example I-1

(Preparation of Thiol Composition Added the Predetermined Amount ofNitrogen-Containing Compound (B-1))

The predetermined amount of the nitrogen-containing compound (B-1) whichwas fractionated in advance was added to the polythiol composition thatis primarily comprised of the polythiol compound (A-1), the ratio of thepeak area of the nitrogen-containing compound (B-1) to the polythiolcompound (A-1) was analyzed by high performance liquid chromatography inaccordance with the conditions described above. The results are shown inTable-2.

(Viscosity Measurement of Polymerizable Composition)

The producing time of the polymerizable composition was set to 0 hourand the viscosity after 7 hours was evaluated as an index.

52 parts by weight of m-xylylene diisocyanate, 0.015 parts by weight ofdibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by KYODO CHEMICAL CO., LTD.; ultraviolet absorbing agent)were mixed and dissolved at 20° C. 48 parts by weight of the polythiolcomposition which is primarily comprised of the obtained polythiolcompound (A-1) was charged and mixed to set to a mixed homogeneousliquid. The producing time of the mixed homogeneous solution was set to0 hour and the viscosity after 7 hours was evaluated by a Brookfieldtype viscometer. The results are shown in Table-2.

(Manufacturing Plastic Lens)

52 parts by weight of m-xylylene diisocyanate, 0.015 parts by weight ofdibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by KYODO CHEMICAL CO., LTD.; ultraviolet absorbing agent)were mixed and dissolved at 20° C. 48 parts by weight of the polythiolcomposition which is primarily comprised of the obtained polythiolcompound (A-1) was charged and mixed to set to a mixed homogeneousliquid. Then, the homogeneous liquid was degassed at 600 Pa for 1 hour,the homogeneous liquid was put into a mold die consisting of a glassmold and a tape after filtrating using a Teflon (registered trademark)filter of 1 μm. The mold die was put into an oven, gradually heated upfrom 10° C. to 120° C., and polymerized for 20 hours. After thepolymerization was finished, the mold die was taken out from the oven toobtain a resin by releasing from the mold die. The obtained resin wasfurther annealed at 120° C. for 3 hours. Physical properties of theobtained plastic lens are shown in Table-2.

TABLE 2 Ratio of Evaluation of resin peak area of loss nitrogen-Viscosity degree of containing after 7 trans- compound hours Colorparency Stria- (B-1) (mPa · s) YI % tion Example I-1 0.8 44 4.6 19 ∘ I-21.2 50 4.6 19 ∘ I-3 1.8 84 4.5 22 ∘ I-4 2.8 117  4.5 23 ∘ ComparativeI-1 3.2 1000<  4.3 25 x Example

The ratio of the peak area of the nitrogen-containing compoundExpression: {[peak area of nitrogen-containing compound (B-1)]/[peakarea of polythiol compound (A-1)]}×100

From the results described above, in a case where the ratio of the peakarea of the nitrogen-containing compound (B-1) to the polythiol compound(A-1) was equal to or less than 3.0 as Examples I-1 to I-4, color andthe loss degree of transparency were excellent and striation also didnot occur. Furthermore, the viscosity of the polymerizable compositionafter 7 hours was low and handling characteristics were excellent.

On the other hand, in a case where the ratio of the peak area of thenitrogen-containing compound (B-1) was over 3.0 as Comparative ExampleI-1, since the viscosity of the polymerizable composition after 7 hourswas over 1,000 mPa·s, it became clear that manufacturing stability ofthe plastic lens was also affected.

Example C-1 (Synthesis of Polythiol Composition which is PrimarilyComprised of bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol)

51.2 parts by weight of 2-mercaptoethanol, 26.5 parts by weight ofdegassed water (the concentration of dissolved oxygen is 2 ppm), and0.16 parts by weight of 49% by weight sodium hydroxide aqueous solutionwere charged into a reaction vessel. 61.99 parts by weight ofepichlorohydrin was added dropwise and charged from 9° C. to 11° C. over6.5 hours, and continuously, stirring was performed for 60 minutes. Froman NMR data, the production of1-chloro-3-(2-hydroxyethylthio)-2-propanol was confirmed.

Next, 150.0 parts by weight of 17.3% sodium sulphide aqueous solutionwas added dropwise and charged from 7° C. to 37° C. over 5.5 hours andstirred for 120 minutes. From an NMR data, the production of a tetraolcompound of the formula (4) was confirmed. Then, 279.0 parts by weightof 35.5% hydrochloric acid was charged, and then 125.8 parts by weightof the purity of 99.90% of thiourea was charged and stirred at 110° C.for 3 hours under reflux to convert into a thiuronium salt. Aftercooling to 45° C., 214.0 parts by weight of toluene was added and cooledto 26° C., 206.2 parts by weight of 25% by weight aqueous ammoniasolution was charged from 26° C. to 50° C. over 30 minutes and stirredfrom 50° C. to 65° C. for 1 hour, and a toluene solution of thepolythiol composition which is primarily comprised of4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane and5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane was obtained.The toluene solution was added into 59.4 parts by weight of 36%hydrochloric acid and acid washing which was performed from 34° C. to39° C. for 30 minutes was conducted twice. 118.7 parts by weight ofdegassed water (the concentration of dissolved oxygen is 2 ppm) wasadded and washing which was performed from 35° C. to 45° C. for 30minutes was conducted five times. After toluene and trace water wereremoved under heating and reduced pressure, filtration under reducedpressure was performed by PTFE type membrane filter of 1.2 μm to obtain115.9 parts by weight of the polythiol composition which is primarilycomprised of 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane(hereinafter, compound A),4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane (hereinafter,compound B), and5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane (hereinafter,compound C) (an isomer mixture of compound A/B/C=85/5/10 (molar ratio)).Physical properties of the obtained polythiol composition are shown inTable-3.

Polythiol comprised of the isomers was respectively isolated andidentified by reversed phase chromatography. Firstly, the results ofelementary analysis, IR, MS and NMR of the compound A are shown.

<Elementary Analysis>

Measured value (%) Calculated value (%) C 32.7 32.8 H 6.2 6.1 S 61.161.2

<IR ν_(max) (KBr) cm⁻¹> 2543 (SH)

<MS> m/z=366 (M⁺)

<¹³C-NMR CDCl₃> δ ppm

a₁ = 24.9 a₂ = 35.1 a₃ = 38.5 a₄ = 48.7 a₅ = 35.9

Next, the results of NMR of the compound C are shown. The results ofelementary analysis, IR and MS were the same as the compound A.

<¹³C-NMR CDCl₃> δ ppm

c₁ = 24.7 c₂ = 35.5 c₃ = 36.8 c₄ = 49.4 c₅ = 28.6

Lastly, the results of NMR of the compound B are shown. The results ofelementary analysis, IR and MS were the same as the compound A.

<13C-NMR CDCl3> δ ppm

b₁ = 24.9 b₂ = 35.1 b₃ = 28.5 b₄ = 48.7 b₅ = 35.9 b₆ = 28.6 b₇ = 49.4 b₈= 36.8 b₉ = 35.5 b₁₀ = 24.7 

(Fractionation and Structure Confirmation)

The nitrogen-containing compound (referred to as B-2) included in thepolythiol composition was fractionated from the polythiol compositionwhich is primarily comprised of the polythiol compound (referred to asA-2) comprised of5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane by performingpreparative high performance liquid chromatography.

From the results of instrumental analysis, it was proved that thenitrogen-containing compound (B-2) had a structure in which one of amercapto group of the polythiol compound (A-2) consisting of5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane was replacedwith a group represented by the following formula (a), furthermore,other one of a mercapto group was replaced with a hydroxyl group. In thefollowing formula (a), * represents an atomic bonding.

The results of an analysis of the nitrogen-containing compound (B-2)included in the polythiol composition are shown.

(1) Mass spectrum

FAB-MS: m/z476 (M⁺) (Matrix m-NBA)

(2) IR (Universal ATR method):

3329, 3198 cm⁻¹: NH stretching, 2539 cm⁻¹: SH stretching, 1606 cm⁻¹: C═Nstretching, 1525 cm⁻¹: NH vending.

(3)¹H-NMR (CDCl₃):

δ ppm 1.6-1.8 (4H (SH)), 2.5-3.5 (33H (—CH₂—, —CH—)), 3.8-3.9 (3H(—CHOH, CH₂OH)).

(4)¹³C-NMR (CDCl₃):

δ ppm 25-39 (CH₂), 48-50 (CH), 61 (CH₂—OH (C adjacent to 0), 69-70(CH—OH (C adjacent to O)), 166, 180 (—C—N— (C of a triazine skeleton)).

The ratio of the peak area of the nitrogen-containing compound (B-2) tothe polythiol compound (A-2) was determined in the following manner.

1. Measurement Conditions of High Performance Liquid Chromatography

Column: YMC-Pack ODS-A A-312 (S5Φ6 mm×150 mm)

Mobile phase: acetonitrile/0.01 mol-potassium dihydrogen phosphateaqueous solution=60/40 (vol/vol)

Column temperature: 40° C.

Flow rate: 1.0 ml/min

Detector: UV detector, wavelength 230 nm

Preparation of measurement solution: 160 mg of a sample is dissolved andmixed in 10 ml of acetonitrile.

Injection volume: 2 μL

2. Ratio of Peak Area of Nitrogen-Containing Compound (B-2)

The composition ratio of the polythiol composition which was produced inExample C-1 was calculated using the following expression.Expression: {[peak area of nitrogen-containing compound (B-2)]/[peakarea of polythiol compound (A-2)]}×100

The result calculated using the expression for computation describedabove was 1.16.

Moreover, the retention times of the polythiol compound (A-2) and thenitrogen-containing compound (B-2) were as follows. A chart of highperformance liquid chromatography is shown in FIG. 2.

Polythiol compound (A-2): From 22.0 minutes to 28.0 minutesNitrogen-containing compound (B-2): From 6.5 minutes to 8.0 minutes

(Manufacturing Plastic Lens)

50.7 parts by weight of m-xylylene diisocyanate, 0.01 parts by weight ofdibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by KYODO CHEMICAL CO., LTD.; ultraviolet absorbing agent)were mixed and dissolved at 20° C. 49.3 parts by weight of the polythiolcomposition which is primarily comprised of the obtained polythiolcompound (A-2) was charged and mixed to set to a mixed homogeneousliquid. After the homogeneous liquid was degassed at 600 Pa for 1 hour,the homogeneous liquid was put into a mold die consisting of a glassmold and a tape after filtrating using a Teflon (registered trademark)filter of 1 μm. The mold die was put into an oven, gradually heated upfrom 10° C. to 120° C., and polymerized for 20 hours. After thepolymerization was finished, the mold die was taken out from the oven toobtain a resin by releasing from the mold die. The obtained resin wasfurther annealed at 130° C. for 4 hours. Physical properties of theobtained lens are shown in Table-3.

Examples C-2 to C-10

The polythiol composition which is primarily comprised of the polythiolcompound (A-2) in the same way as Example C-1 except setting to theproducing conditions described in Table-3 was produced and the plasticlens was manufactured. The results are shown in Table-3.

Example D-1 (Synthesis of Polythiol Composition which is PrimarilyComprised of bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol)

51.2 parts by weight of 2-mercaptoethanol, 26.5 parts by weight ofdegassed water (the concentration of dissolved oxygen is 2 ppm), and0.16 parts by weight of 49% by weight sodium hydroxide aqueous solutionwere charged into a reaction vessel. 61.99 parts by weight ofepichlorohydrin was added dropwise and charged from 9° C. to 13° C. over6.5 hours, and continuously, stirring was performed for 40 minutes. Froman NMR data, the production of1-chloro-3-(2-hydroxyethylthio)-2-propanol was confirmed.

Next, 150.0 parts by weight of 17.3% sodium sulphide aqueous solutionwas added dropwise and charged from 5° C. to 42° C. over 4.5 hours, andcontinuously, stirring was performed for 40 minutes. From an NMR data,the production of a tetraol compound of the formula (4) was confirmed.Next 117.4 parts by weight of the purity of 99.90% of thiourea wascharged, 84.3 parts by weight of the purity of 90.7% of hydrochloricacid gas was blown and stirred at 110° C. for 3 hours under reflux toconvert into a thiuronium salt. After cooling to 45° C., 214.0 parts byweight of toluene was added and cooled to 26° C., 158.4 parts by weightof 25% by weight aqueous ammonia solution was charged from 26° C. to 46°C. over 25 minutes and matured from 54° C. to 62° C. for 1 hour, and atoluene solution of the polythiol composition which is primarilycomprised of the polythiol compound (A-2) consisting of5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane and4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane was obtained.59.4 parts by weight of 36% hydrochloric acid was added into the toluenesolution and acid washing which was performed from 33° C. to 40° C. for30 minutes was conducted twice. 118.7 parts by weight of degassed water(the concentration of dissolved oxygen is 2 ppm) was added and washingwhich was performed from 35° C. to 45° C. for 30 minutes was conductedfive times. After toluene and trace water were removed under heating andreduced pressure, filtration under reduced pressure was performed byPTFE type membrane filter of 1.2 μm to obtain 115.0 parts by weight ofthe polythiol composition which is primarily comprised of the polythiolcompound (A-2). Physical properties of the obtained polythiolcomposition are shown in Table-3. The identification of the polythiolcompounds was performed by an NMR, and the same results as Example C-1were obtained.

(Fractionation and Structure Confirmation)

The nitrogen-containing compound (referred to as B-2) included in thepolythiol composition was fractionated from the polythiol compositionwhich is primarily comprised of the polythiol compound (A-2) byperforming preparative high performance liquid chromatography.

From the results of instrumental analysis, it was proved that thenitrogen-containing compound (B-2) had a structure in which one of amercapto group of the polythiol compound (A-2) was replaced with a grouprepresented by the following formula (a), furthermore, other one of amercapto group was replaced with a hydroxyl group. In the followingformula (a), * represents an atomic bonding.

The results of an analysis of the nitrogen-containing compound (B-2)included in the polythiol composition are shown.

(1) Mass spectrum

FAB-MS: m/z476 (M⁺) (Matrix m-NBA)

(2) IR (Universal ATR method):

3329, 3198 cm⁻¹: NH stretching, 2539 cm⁻¹: SH stretching, 1606 cm⁻¹: C═Nstretching, 1525 cm⁻¹: NH vending.

(3)¹H-NMR (CDCl₃):

δ ppm 1.6-1.8 (4H (SH)), 2.5-3.5 (33H (—CH₂—, —CH—)), 3.8-3.9 (3H(—CHOH, CH₂OH)).

(4)¹³C-NMR (CDCl₃):

δ ppm 25-39 (CH₂), 48-50 (CH), 61 (CH₂—OH (C adjacent to 0)), 69-70(CH—OH (C adjacent to 0)), 166, 180 (—C—N—(C of a triazine skeleton)).

The ratio of the peak area of the nitrogen-containing compound (B-2) tothe polythiol compound (A-2) was determined by performing in the sameway as Example C-1.

(Manufacturing Plastic Lens)

50.7 parts by weight of m-xylylene diisocyanate, 0.01 parts by weight ofdibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by KYODO CHEMICAL CO., LTD.; ultraviolet absorbing agent)were mixed and dissolved at 20° C. 49.3 parts by weight of the polythiolcomposition which is primarily comprised of the obtained polythiolcompound (A-2) was charged and mixed to set to a mixed homogeneousliquid. After the homogeneous liquid was degassed at 600 Pa for 1 hour,the homogeneous liquid was put into a mold die consisting of a glassmold and a tape after filtrating using a Teflon (registered trademark)filter of 1 μm. The mold die was put into an oven, gradually heated upfrom 10° C. to 120° C., and polymerized for 20 hours. After thepolymerization was finished, the mold die was taken out from the oven toobtain a resin by releasing from the mold die. The obtained resin wasfurther annealed at 130° C. for 4 hours. Physical properties of theobtained lens are shown in Table-3.

Examples D-2 to D-10

The polythiol composition which is primarily comprised of the polythiolcompound (A-2) in the same way as Example D-1 except setting to theproducing conditions described in Table-3 was produced and the plasticlens was manufactured. The results are shown in Table-3.

TABLE 3 Condi- Condition III Monomer analysis value tion I Condition IIAcid Acid Ratio Evaluation of resin Dio- Charg- wash- wash- of peak lossde- lated ing Charg- ing ing Spe- Re- area of gree of temper- temper-ing concen- temper- cific Acid- Wa- Vis- frac- nitrogen- Col- trans-ature ature time tration ature Col- Grav- ity ter cosity tive NH₄containing or parency Stria- ° C. ° C. Minute % ° C. or ity ppm ppm mPa· s index ppm compound YI % tion Example 9-11 26-50 30 36 34-39 15 1.29024 80 212 1.6474 0.03 1.16 4.4 23 ◯ C-1 Example 9-13 26-50 28 36 35-4015 1.289 22 90 208 1.6473 0.03 1.08 4.4 21 ◯ C-2 Example 9-12 26-50 2836 35-40 15 1.290 27 40 210 1.6476 0.02 1.09 4.4 22 ◯ C-3 Example 9-1326-50 28 36 35-40 15 1.290 24 70 209 1.6476 0.04 1.11 4.4 22 ◯ C-4Example 9-12 26-50 28 36 35-40 15 1.290 25 50 208 1.6475 0.02 1.18 4.323 ◯ C-5 Example 9-12 26-50 28 36 35-40 15 1.290 22 50 209 1.6474 0.041.18 4.4 21 ◯ C-6 Example 9-12 26-50 28 36 35-40 15 1.290 23 80 2081.6477 0.01 1.17 4.4 21 ◯ C-7 Example 9-12 26-50 30 36 35-40 15 1.288 2290 209 1.6474 0.03 1.15 4.4 21 ◯ C-8 Example 9-12 26-50 28 30 35-39 151.290 26 60 214 1.6476 0.03 1.25 4.4 22 ◯ C-9 Example 9-13 26-50 30 3035-39 15 1.290 25 20 215 1.6475 0.03 1.30 4.5 23 ◯ C-10 Example 9-1326-46 25 36 33-40 10 1.290 12 20 206 1.6474 0.02 1.20 4.0 18 ◯ D-1Example 9-15 26-47 25 36 31-37 10 1.290 11 20 206 1.6474 0.03 0.97 4.018 ◯ D-2 Example 9-13 26-47 25 36 31-37 10 1.290 14 40 208 1.6474 0.021.10 4.2 18 ◯ D-3 Example 8-13 26-47 25 36 32-37 10 1.290 14 30 2081.6474 0.04 1.17 4.2 17 ◯ D-4 Example 9-14 26-47 25 36 32-37 10 1.290 1240 208 1.6474 0.02 1.08 4.0 17 ◯ D-5 Example 9-12 26-48 25 36 31-37 101.290 19 60 213 1.6474 0.03 1.45 4.2 18 ◯ D-6 Example 9-14 26-49 25 3631-37 10 1.290 19 40 215 1.6474 0.03 1.39 4.2 18 ◯ D-7 Example 9-1326-47 25 36 33-37 10 1.290 17 50 213 1.6473 0.02 1.20 4.1 19 ◯ D-8Example 5-15 26-47 25 30 32-36 10 1.290 14 60 208 1.6472 0.02 1.19 4.119 ◯ D-9 Example 9-13 26-48 25 30 32-39 10 1.290 14 20 208 1.6471 0.021.16 4.2 20 ◯ D-10 Condition I: Conditions of reacting 2-mercaptoethanolwith epichlorohydrin. Condition II: Conditions of charging an ammoniaaqueous solution in a hydrolysis reaction. Condition III: Conditions ofhydrochloric acid washing. Ratio of peak area of nitrogen-containingcompound: Expression {[peak area of nitrogen-containing compound(B-2)]/[peak area of polythiol compound (A-2)]} × 100

Examples II-1 to 11-3, Comparative Example II-1

(Preparation of Thiol Composition Added the Predetermined Amount ofNitrogen-Containing Compound (B-2))

The predetermined amount of the nitrogen-containing compound (B-2) whichwas fractionated in advance was added to the polythiol composition thatis primarily comprised of the polythiol compound (A-2), the ratio of thepeak area of the nitrogen-containing compound (B-2) was analyzed by highperformance liquid chromatography in accordance with the conditionsdescribed above. The results are shown in Table-4.

(Viscosity Measurement of Polymerizable Composition)

The producing time of the polymerizable composition was set to 0 hourand the viscosity after 7 hours was evaluated as an index.

50.7 parts by weight of m-xylylene diisocyanate, 0.015 parts by weightof dibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by KYODO CHEMICAL CO., LTD.; ultraviolet absorbing agent)were mixed and dissolved at 20° C. 49.3 parts by weight of the polythiolcomposition which is primarily comprised of the obtained polythiolcompound (A-2) was charged and mixed to set to a mixed homogeneousliquid. The producing time of the mixed homogeneous solution was set to0 hour and the viscosity after 7 hours was evaluated by a Brookfieldtype viscometer. The results are shown in Table-4.

(Manufacturing Plastic Lens)

50.7 parts by weight of m-xylylene diisocyanate, 0.01 parts by weight ofdibutyltin dichloride as a curing catalyst, 0.10 parts by weight ofZELEC UN (trade name, a product manufactured by Stepan Company; acidicphosphoric ester), 0.05 parts by weight of Viosorb 583 (trade name,manufactured by CHEMICAL CO., LTD. ultraviolet absorbing agent) weremixed and dissolved at 20° C. 49.3 parts by weight of the polythiolcomposition which is primarily comprised of the obtained polythiolcompound (A-2) was changed and mixed to set to a mixed homogeneousliquid. After the homogeneous liquid was degassed at 600 Pa for 1 hour,the homogeneous liquid was put into a mold die consisting of a glassmold and a tape after filtrating using a Teflon (registered trademark)filter of 1 μm. The mold die was put into an oven, gradually heated upfrom 10° C. to 120° C., and polymerized for 20 hours. After thepolymerization was finished, the mold die was taken out from the oven toobtain a resin by releasing from the mold die. The obtained resin wasfurther annealed at 130° C. for 4 hours. Physical properties of theobtained plastic lens are shown in Table-4.

TABLE 4 Ratio of Evaluation of resin peak area of Loss nitrogen-Viscosity degree of containing after Col- trans- compound 7 hours orparency Stria- (B-2) (mPa · s) YI % tion Example II-1 0.75 175 4.1 23 ◯II-2 1.50 209 4.1 22 ◯ II-3 2.80 569 4.3 30 ◯ Comparative II-1 3.201000< 4.3 28 X Example

Ratio of peak area of nitrogen-containing compoundExpression: {[peak area of nitrogen-containing compound (B-2)]/[peakarea of polythiol compound (A-2)]}×100

From the results described above, in a case where the ratio of the peakarea of the nitrogen-containing compound (B-2) to the polythiol compound(A-2) was 3.0 or less as Examples II-1 to 11-3, color and the lossdegree of transparency were excellent and striation also did not occur.Furthermore, the viscosity of the polymerizable composition after 7hours was low and handling characteristics were excellent.

On the other hand, in a case where the ratio of the peak area of thenitrogen-containing compound (B-2) was over 3.0 as Comparative ExampleII-1, since the viscosity of the polymerizable composition after 7 hourswas over 1,000 mPa·s, it became clear that manufacturing stability ofthe plastic lens was also affected.

The invention claimed is:
 1. A polythiol composition comprising: apolythiol compound (a) represented by the following formula (5)

and a compound (b) wherein, in a high performance liquid chromatographymeasurement of the polythiol composition under the following conditions,the peak area of the compound (b) which appears at the retention timefrom 4.3 minutes to 5.6 minutes is equal to or less than 3.0, withrespect to the peak area of 100 of the polythiol compound (a) whichappears at the retention time from 12.0 minutes to 13.5 minutes,(Measurement conditions) Column: YMC-Pack ODS-A A-312 (S5Φ6 mm×150 mm)Mobile phase: acetonitrile/0.01 mol-potassium dihydrogen phosphateaqueous solution=60/40 (vol/vol) Column temperature: 40° C. Flow rate:1.0 ml/min Detector: UV detector, wavelength 230 nm Preparation ofmeasurement solution: 160 mg of a sample is dissolved and mixed in 10 mlof acetonitrile Injection volume: 2 μL.
 2. The polythiol compositionaccording to claim 1, wherein the peak area of the compound (b) whichappears at the retention time from 4.3 minutes to 5.6 minutes is 0.01 to3.0, with respect to the peak area of 100 of the polythiol compound (a)which appears at the retention time from 12.0 minutes to 13.5 minutes.3. The polythiol composition according to claim 1, wherein the peak areaof the compound (b) which appears at the retention time from 4.3 minutesto 5.6 minutes is equal to or less than 1.0, with respect to the peakarea of 100 of the polythiol compound (a) which appears at the retentiontime from 12.0 minutes to 13.5 minutes.
 4. The polythiol compositionaccording to claim 1, wherein the peak area of the compound (b) whichappears at the retention time from 4.3 minutes to 5.6 minutes is equalto or less than 0.50, with respect to the peak area of 100 of thepolythiol compound (a) which appears at the retention time from 12.0minutes to 13.5 minutes.
 5. The polythiol composition according to claim1, wherein the compound (b) contains a compound having following resultof a IR measurement by Universal ATR method (Result of the IRmeasurement) 3300 cm⁻¹: NH stretching, 2541 cm⁻¹: SH stretching, 1606cm⁻¹: C═N stretching, 1520 cm⁻¹: NH vending.
 6. A process for producinga polythiol composition comprising: a step of reacting 2mercaptoethanolwith an epihalohydrin compound represented by the following formula (1)to obtain a polyalcohol compound represented by the following formula(2),

wherein X is a halogen atom,

a step of reacting the polyalcohol compound represented by the formula(2) with thiourea to obtain an isothiuronium salt, a step of hydrolyzingthe isothiuronium salt to obtain a polythiol composition containing apolythiol compound (a) represented by the following formula (5) and acompound (b),

and a step of acid-washing the obtained polythiol composition undertemperature of 10° C. to 50° C. to obtain following polythiolcomposition, wherein, in a high performance liquid chromatographymeasurement of the polythiol composition obtained by acid-washing stepunder the following conditions, the peak area of the compound (b) whichappears at the retention time from 4.3 minutes to 5.6 minutes is equalto or less than 3.0, with respect to the peak area of 100 of thepolythiol compound (a) which appears at the retention time from 12.0minutes to 13.5 minutes, (Measurement conditions) Column: YMC-Pack ODS-AA-312 (S5Φ6 mm×150 mm) Mobile phase: acetonitrile/0.01 mol-potassiumdihydrogen phosphate aqueous solution=60/40 (vol/vol) Columntemperature: 40° C. Flow rate: 1.0 ml/min Detector: UV detector,wavelength 230 nm Preparation of measurement solution: 160 mg of asample is dissolved and mixed in 10 ml of acetonitrile.
 7. The processfor producing a polythiol composition according to claim 6, whereintemperature is 15° C. to 50° C. in the acid-washing step.
 8. The processfor producing a polythiol composition according to claim 6, whereintemperature is 20° C. to 50° C. in the acid-washing step.
 9. The processfor producing a polythiol composition according to claim 6, whereintemperature is 30° C. to 45° C. in the acid-washing step.
 10. Apolymerizable composition for an optical material comprising: thepolythiol composition according to claim 1; and a poly(thio)isocyanatecompound.
 11. A method of manufacturing a molded product, comprising: astep of mixing the polythiol composition according to claim 1 and apoly(thio)isocyanate compound to obtain a polymerizable composition foran optical material; and a step of injecting the polymerizablecomposition into a mold and curing the composition.
 12. A molded productwhich is obtained by curing the polymerizable composition according toclaim
 10. 13. An optical element comprised of the molded productaccording to claim
 12. 14. A lens comprised of the optical elementaccording to claim 13.